Development of the permanent magnet synchronous motor with optimal rotor construction

本文的目的是推导出一个最佳的永磁同步电动机（PMSM）的转子结构。永磁同步电动机的励磁系统通常是一个主磁极只有一个磁铁，而我们将主磁极的磁铁替换成多个具有相同极性的子磁铁。每个子磁体的尺寸和布置基于脉宽调制（PWM）的概念。通过采用所提出的子磁体方案，我们不仅可以减少电机中的气隙磁场的不期望的高次空间谐波，而且还为相邻子磁体之间的阻尼绕组提供空间。从混合FE-BE的研究来看，（有限元与边界元耦合）方法和实验，我们从以下几个方面证明了所提出的结构在实际应用中是有效的：气隙磁通分布中基波的大小，高次空间谐波与基波分量的比率，制造的可行性，振荡，通过分析和实验，得出了如下结论：1.子磁体数目越多，产生的空间谐波越少，阻尼效果越好。采用高品位的稀土永磁体可以补充分磁降低气隙磁通的作用.阻尼效果受转子杆条总数的影响较大.将电路和运动方程同时应用于混合有限元边界元法中，可以提高分析精度，从以上优点可以看出，六分型结构是所研究的结构中最理想的结构。但考虑到制造上的困难，我们也建议四分型在实际应用中是有效的。

The purpose of this paper is to derive an optimal rotor construction in the permanent magnet synchronous motor (PMSM). While the field system of PMSM has generally a single magnet for a mainpole, we replace the magnet into plural sub-magnets having same polarity instead of the single one. The dimensions and arrangements of each sub-magnet are based on the concept of pulse width modulation (PWM). By adopting the proposed sub-magnet scheme, we can not only reduce the undesirable higher space harmonics of the air-gap field in electric machinery but also provide space for damper winding between neighboring sub-magnets. From the investigation by hybrid FE-BE (coupled finite element and boundary element) method and experiment, we presented that the proposed construction is effective for practical use in view of the followings : the magnitude of fundamental in air-gap flux distribution, the ratio of higher space harmonics to the fundamental component, the feasibility of manufacture, the hunting oscillations, and the induction starting.The obtained results by analysis and experiment are as follows.1. The more number of sub-magnets produces the less space harmonics and the higher damping effects. The reduction of air-gap flux by magnet division can be supplemented by adopting the high grade of rare-earth one.2. The damping effects are much influenced by whole amount of rotor bars.3. By applying both electric circuit and motion equation to the hybrid FE-BE method, the precision of analysis could be improved.From the above advantages, we conclude that six-divided type is the most desirable construction among the investigated types. However, considering the difficulties of manufacture, we also propose that four-divided type is effective for practical use.